Reflection of atoms by light

The atom mirror is the key element of matter-wave optics. An electromagnetic mirror for neutral atoms was suggested by Cook and Hill (1982). The idea was to use the radiation force of an evanescent laser wave outside a dielectric surface to repel slow atoms. This evanescent-wave atomic mirror was realized experimentally by Balykin et al. (1988a). 

1 The laser field and atomic potential in a evanescent wave 

Let us first consider the scheme suggested by Cook and Hill (1982). When a plane traveling light wave is totally reflected internally at the surface of a dielectric in a vacuum, a evanescent wave is generated on the surface (Fig. 7.1). By application of Fresnel s reflection formulas (Born and Wolf 1984), the intensity of evanescent wave is given by 

The reflection of an atom from a mirror may also be considered as the result of its being expelled out of a potential field, whose energy, according to eqn (6.1), is 

In the reflection of atoms by an evanescent wave, the amplitude of the light field does not necessarily change adiabatically slowly in comparison with the relaxation of the internal atomic motion. In this case eqn (7.6) for the light gradient (dipole) force acting on the atom is only the zeroth-order term in an expansion of the force in powers of the inverse interaction time (Ol shanii et al. 1992). The next term in the expansion gives rise to a dissipative part in the gradient force. Such nonadiabaticity can happen if the time of interaction of the atom with the field is comparable to 7 F In this case the specular character of the reflection of atoms can be disturbed. 

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